Product from Secret Labs

Netduino is an open source electronics platform using the .NET Micro
Framework. Featuring a 32-bit microcontroller and a rich development
environment, it is suitable for engineers and hobbyists alike. This
combines the ease of high-level coding and the raw features of
microcontrollers. Enjoy event-based programming, multi-threading,
line-by-line debugging, breakpoints and more!

The
netduino GO! Shield base module is a module which gives you a full
fledged netduino (minus barrel jack and usb) using only one of your
netduino GO! sockets. The virtualization technology on the netduino GO!
allows you to use the shield base as a netduino, and your shields won't
know the difference!

The Shield Base adds Arduino
shield pin compatibility to your Netduino Go. Just plug it in and access
InputPorts, OutputPorts, AnalogInputs, PWMs, and more using standard C#
or Visual Basic code.

and twice the available RAM (100KB+) of Netduino Plus.
And with Netduino Go, we've virtualized all the peripherals. So you
simply pick what you need and plug it in. Each module has a small
microchip which works together with the mainboard.
Want to use a relay? Just plug it in. Need six RGB LEDs? No problem. How
about a touchscreen? One cable, plug and play.